1. Field of the Invention
The present invention relates to a rotary dresser having diamond abrasive grains arranged on an outer circumference of a roll.
2. Discussion of the Related Art
Rotary dressers with a plurality of the diamond abrasive grains embedded on an outer circumferential surface of a rotatable roll are well-known as described in, e.g., JP 2009-285776 A. In the rotary dressers of this kind, diamond abrasive grains are usually arranged spirally at a predetermined interval on an outer circumferential surface of a roll, so that the distribution density of the diamond abrasive grains per area is made to be fixed.
As shown in FIG. 7, in a rotary dresser having a roll 4 with cylinder portions 1, 2 at both axial end portions and with a concave arc portion 3 between the cylinder portions 1, 2, the distribution density of diamond abrasive grains 5 is set to be fixed at the arc portion 3. Thus, the number of the diamond abrasive grains 5 which are arranged on the concave arc portion 3 in the circumferential direction differs in dependence on the circumferential length at each of axial positions of the concave arc portion 3. That is, as shown by the graph in the same figure, the number of the diamond abrasive grains 5 in the circumferential direction (i.e., the quantity of diamond in the circumferential direction) becomes smaller at a small-diameter portion of the arc portion 3, while the number of the diamond abrasive grains 5 in the circumferential direction becomes larger as the axial position comes close to each of both end portions on the arc portion 3.
As a result, the number of the diamond abrasive grains which act on a grinding wheel per rotation of the dresser is increased at a portion that has a large number of the diamond abrasive grains in the circumferential direction. This results in increasing the dressing resistance at that portion and hence, in causing grinding burns to be liable to be generated on the grinding wheel. On the other hand, the number of the diamond abrasive grains which act on the grinding wheel per rotation of the dresser is decreased at another portion that has a small number of the diamond abrasive grains in the circumferential direction. Thus, the diamond abrasive grains at such another portion become larger in wear than those at the portion having the large number of diamond abrasive grains, and this gives rise to a problem that local wear or abrasion are liable to occur.